Say the theaters themselves didn't start pulling this.
I think "The Interview" would've actually done pretty well. Why? Because it's aimed at your 20-40 year old male demographics. A type of demographic that isn't just likely to ignore such a "threat", but the type to do the action simply as a means to either thumb their nose at the hackers or to puff their chest out for a feeling of false bravado. It also seemingly enticed some that normally wouldn't fall in that demographic or normally wouldn't want to see the movie to want to go based on the basic nature of political stubborness some have.
I imagine a big amount of Christmas Day movie traffic are families, likely going to more family oriented movies (or letting the kids go off to one while the adults go to another). I think there's a fair bit of people in those demographics that absolutely WOULD be turned off by these threats and make a decision to just wait for another day to go see the totally unrelated movie they were going to go see. And I have a feeling those numbers would've been more damaging to the theaters than the number of people flooding in to see The Interview.